SB-10 USER'S MANUAL

Serial busy protocols
In these protocols, the printer uses DTR (pin 20) and REV-CH (pin
11) to signal to the computer when it is able to accept data. These
pins go on when the printer is ready to accept data. In the l-byte
mode, they go off after each character is received. In the l-block
mode, they go off only as the printer buffer approaches capacity.
In both cases, they stay off if the buffer is too full to accept more data.
XONIXOFF protocol
This protocol uses the ASCII characters DC1 and DC3 (sometimes
called XON and XOFF, respectively) to communicate with the corn- -
puter. When the printer buffer approachescapacity, the printer sends
a DC3 on TXD (pin 2) to tell the computer that it must stop sending --
data. When the printer is able to receive more data, it sends a DC1
on the TXD pin. The computer can then send more data until the - --
printer sends another DC3.
ACK protocol
-
In the ACK protocol, the printer sends an ACK (ASCII 6) signal on
the TXD pin each time it is prepared to receive a byte of data.
• THE IEEE-488 INTERFACE
You may also use the IEEE-488 interface to connect printer to your
computer. This 8-bit parallel interface uses a TTL-compatible logic
level, and is capable of transferring characters at rates of up to 1
megabyte per second. Its transfer system is governed by a three-wire
handshaking protocol, illustrated in Figure H-4.
NRFD
(LIstenerI
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Data Walt
------DataProcessing
Data Invalid
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DAV
(Talker)
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--- --_- ------Data”a,,,,
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NDAC
lLlrtenerl
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-------- DataReceptionComplete
Data not yet recewed or
currenfly bemg received
Figure H-4. Data transfer timing chart for the IEEE-488 interface.
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